People affected by the Holocaust directly who are still alive are all getting up there in age, and their families are going to be old already, too, but there are other lasting effects such as the founding of the modern nation of Israel. That's relevant because of all the current tension in that part of the world. And the American Civil War could be said to be still relevant because of the cultural differences between the American South and other parts of the country.

I guess I'd say that as long as someone is using history to justify their actions then we'll need to keep that history alive, either to justify our claims or to refute someone else's.

"The trouble with fighting for human freedom is that one spends most of one's time defending scoundrels. For it is against scoundrels that oppressive laws are first aimed, and oppression must be stopped at the beginning if it is to be stopped at all." - H. L. Mencken, unsourced

"There is a cult of ignorance in the United States, and there always has been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'"- Isaac Asimov, Column in Newsweek (21 January 1980) [source]